Knitting machine yarn feeding apparatus

ABSTRACT

Textile yarn is withdrawn from a yarn package as demanded for knitting by a plurality of needles forming a portion of a knitting machine producing textile fabric, through selected correlation of signals indicating the speed of the knitting machine and the speed of yarn supply or indicating the tension of yarn being supplied and the desired tension level for yarn to be supplied.

l/nite States Patent 11 1 White et al.

[ KNITTING MACHINE YARN FEEDING APPARATUS [76] Inventors: Eugene F.White; Frances H. While, both of 600 S. Church St., Monroe, NC. 28110 22Filed: July 23,1973

121 Appl. NO.Z 381,629

52 us. 01 66/132 R, 66/146, 66/163, 242/45 51 Int. Cl D04b 15/48 581Field 61 Search 66/146, 132 R, 125 R, 163; 1 242/45 [56] ReferencesCited UNITED STATES PATENTS 3,324.685 6/1967 Schmidt et al. 66/132 R3.321499 6/1967 Schmidt et a1.......l 66/132 R 1451 Jan. 7, 19753,680,753 8/1972 Shaw-Stewart 242/45 3,781,532 12/1973 Dorsman et al66/125 R X FOREIGN PATENTS OR APPLICATIONS 7,003,501 9/1970 Netherlands66/146 Primary Examin'erWm. Carter Reynolds Attorney, Agent, orFirm-Parrott:, Bell, Seltzer, Park & Gibson [57] ABSTRACT Textile yarnis withdrawn from a yarn package as demanded for knitting by a pluralityof needles forming a portion of a knitting machine producing textilefabric, through selected correlation of signals indicating the speed ofthe knitting machine and the speed of yarn supply or indicating thetension of yarn being supplied and the desired tension level for yarn tobe supplied.

7 Claims, 1 Drawing Figure mssma Fake-med Jan. 7, 1975 KNITTING MACHINEYARN FEEDING. APPARATUS Difficulties of supplying yarn to a knittingmachine forming a textile fabric in such a manner as to assure desireduniformity in the finished knitted fabric have long been recognized andmany attempts have been made at solutions for these problems. Generally,the approaches which have been proposed have related either tocontrolling the length of yarn delivered to a knitting position during aparticular interval of time and thereby controlling the rate of yarnconsumption or to controlling the tension condition of the yarn which isdelivered and thereby controlling the tension imposed on the yarn as itis supplied to the knitting position. Each of these general approacheshas found acceptance under certain operating conditions relating to thenature of the yarn supplied and the nature of the fabric being knitted.

Heretofore, it has been conventional for an operator of a knittingmachine to determine the type of yarn feed control believed desirablefor the machine and thereafter use the machine in knitting fabrics whichmay be produced acceptably pursuant to such control. Such choicesfrequently are related to the specific type of knitting machineemployedas well as to the types of fabrics to be produced. r The limitationsimposed by such yarn feeding control selection and the growingversatility and use of knitting machines have resulted in an increasingdesire, on the part of knitting machine operators, for the availabilityof a choice as to yarn feeding controls and improved flexibility in sucha choice.

In view of the difficulties and deficiencies which have been pointedout, it is an object of this invention to pro vide a ready selection ofyarn feed in correlation with the rate of yarn consumption by a knittingmachine or in correlation with desired tension conditions at a knittingposition on the knitting machine. In realizing this object of thepresent invention, means are provided for sensing the rate of supply ofyarn and the rate of yarn consumption by the knitting machine. Further,additional means are provided for sensing the tension of yarn beingsupplied and for indicating the desired level of tension for yarn to besupplied. With such indications available, selection is made as to thedesired manner of yarn feeding control and a common variable speed drivemeans is then varied as required.

Yet a further object of this invention is to provide for selecteduniformity of control over a plurality of textile yarns being suppliedto a corresponding plurality of knitting positions on a knittingmachine. Realizing this object of the present invention, selectivity isprovided as to a plurality of levels of control for the plurality ofyarns.

Yet a further object of this invention is to integrate control overinterruption of operation of a knitting ma chine in the event ofbreakage of a yarn being supplied to a knitting position with yarnfeeding controls as discussed above.

Some of the objects of the invention having been stated, other objectswill appear as the description proceeds, when taken in connection withthe accompanying drawings, in which a partly perspective, partlyschematic illustration is presented of yarn feeding apparatus inaccordance with this invention.

While the best mode presently contemplated for the practice of thisinvention will be described hereinafter with particular reference to theaccompanying illustration, it is to be understood at the outset ofthisdescription that the description and illustration are intended to beread broadly. It is contemplated that the present invention may bemodified in detail while embodying the general arrangement of thisinvention and the description and illustration are accordingly to beread broadly and not as limiting upon the scope of this invention.

Referring now particularly to the illustration, the present inventionwill be described with particular refercnce to a circular knittingmachine and to one yarn line by which a textile yarn is supplied to aknitting position of the circular knitting machine. It is to beunderstood that this invention is contemplated as being applicable toforms of knitting machines other than a circular knitting machine andisparticularly contemplated as being applicable to a multiple feedcircular knitting machine such a machine producing double knit fabricfor outerwear. In common with knitting machines gen erally, the knittingmachine with which the apparatus of this invention is illustratedincludes rotating drive member here illustrated as a main drive gear ll.The main drive gear 11 rotates at a speed coordinated with rotation ofthe cylinder which carries a plurality of needles. As is known topersons skilled in the construction and use of circular knittingmachines, the needles are moved during rotation of the cylinder forknitting textile fabric from yarn supplied to knitting position of themachine.

In the illustrated form of this invention, yarn 12 to be knitted intotextile fabric is supplied from a suitable yarn package 14 to knittingmachine positions generally indicated at 15 where the yarn 12 isreceived by needles and knitted into a fabric. Due to the accuratecontrol accomplished by this invention, the package 14 may be of anytype, including dyeing or dyed packages of types not normally suitablefor knitting machine feeding. As is known to persons skilled in theconstruction and use of knitting machines, it is conventional forcertain large circular knitting machines to have a large number of yarnpackages 14 supplying a corresponding .number of yarn 12 to acorresponding number of positions 15. The present illustration setsforth only a single yarn line, for purposes of simplicity, with it beingunderstood that it is contemplated that parallel arrange ments would beprovided on other yarn lines.

In order to feed the yarn 12 from the package 141 to the knittingposition 15 in a desired manner as brought out more fully hereinafter,means are interposed between each yarn package 14 and the needles forpositively engaging the corresponding yarn 12. As illustrated, the yarnengaging means preferably comprises a positive grip feed pulley 16,supported for rotation with a drive shaft 17 which is included in anddriven in rotation by a variable speed drive means generally indicatedat 18. The variable speed drive means drives the positive pulley 16 inrotationat a controlled speed, and thereby withdraws yarn 12 fromcorresponding package 14 and feeds the yarn to the needles as requiredfor knitting. It is to be noted that the yarn is fed without addition orremoval of twist and thus the apparatus of this invention isadvantageous forany yarn desired for knitting.

In the form illustrated, the variable speed drive means 18 preferablytakes the form of an electrical servomotor which may be driven atvariable rotational speeds by controlling the characteristics ofelectrical current applied thereto. Several types of such electricalservomotors are known to persons skilled in the electrical control arts,including in motors whose speed is varied by controlling thecharacteristic of pulses supplied thereto and motors whose speed iscontrolled by varying the level of voltage applied thereto. It iscontemplated by this invention that the electrical servomotor employedas the drive means 18 may be selected from among such known forms andwill provide torque sufficient for withdrawing yarn from any type ofpackage.

Operatively connected with the variable speed drive means 18 is a firstcontrol means generally indicated at 20 which controls the rotationalspeed of the drive means 18. In the form illustrated, the first controlmeans 20 comprises a servomotor amplifier which receives electricalcurrent from a suitable source through a supply conductor 21 anddelivers such electrical current (modified as may be required). to theelectrical servomotor through a conductor 22. As will be brought outmore fully hereinafter, the motor amplifier receives an error signalthrough an error signal conductor 24.

In order to accomplish feeding of yarn 12 at a controlled linear rate, atachometer means generally indicated at 25 is provided which isoperatively responsive to the drive means 18 for sensing rotation of thedrive shaft 17 and for generating a first electrical signal indicativeof the speed of rotation thereof. Preferably, and in the formillustrated, the tachometer 25 takes the form of a shaft angle detectorwhich generates a train of pulses coordinated to the angular positionsand thus the rotation of the drive shaft 17. The pulse train thusoriginated by the tachometer means 25 is passed to a frequency tovoltage convertor 26 which may be an appropriate circuit selected fromamong such circuits known to designers of electronics controls. Theresulting output signal from the convertor 26 appears on an outputconductor 28 as a voltage proportional to the rotational speed of thedrive shaft 17. While not here illustrated, it is to be noted that thetrain of pulses from the tachometer 25 may be used to measure lengths ofyarn fed or rates of yarn feed.

In a generally'similar manner, the rotational speed of the rotatingdrive member of the knitting machine is sensed and a second electricalsignal is generated which is indicative of the speed of rotationthereof. In instances, such as that illustrated, where a main drive gear11 is employed, an electromagnetic sensor 29 of an appropriate type maybe positioned adjacent the rotating teeth of the gear 11, to generatethe pulse train which is supplied to a frequency to voltage convertor30. The resulting output appearing at a conductor 31 would be in theform of a voltage proportional to the rotational speed of gear 11. Aswill be understood, the sensor 29 will take other forms, such asphotoelectrical or the like.

In order to accomplish control in accordance with tension condition, thearrangement of this invention further provides a tension sensor 32disposed along the path of travel of the yarn 12 and preferably near theknitting machine position 15. The tension sensor has a series of threepins 34a, 34b, 34c with the yarn l2 trained thereabout so that thetension in the yarn causes fluctuation of the center pin 34b. By meansof a differential transformer or similar arrangement, an electricalsignal appears on an output conductor 35 in the form of a voltageproportional to the level of tension in the yarn 12. A standard means 36at the same time provides a fixed voltage on an output conductor 38,indicative of a desired level of tension for the yarn 12.

In accordance with this invention, a switch generally indicated at 40 isprovided for selecting between coordinated pairs of signals appearing onthe conductors 28, 31, 35 and 38. In the particular position shown, theswitch 40 is arranged for tension control of yarn feeding as receivingthe third and fourth signals appearing respectively on the outputconductor 35 from the tension sensor 32 and the output conductor 38 fromthe standard means 36. In the alternate position, the switch 40 would beconnected to pass the voltages that are present on the conductors 28 and31 and indicative of the rotational speeds of the servomotor and themain drive gear:

In either instance, certain signals passing through the switch means 40are applied along a feed back signal line 41 to a second control meansin a form of comparison circuit 42. Signals passing through the otherleg of the switch means 40 are directed to three level settingpotentiometers 44, 45, 46, which may be adjusted to give a desiredoffset or level shift to tension and speed control. A selected one ofthe three level setting potentiometers 44, 45, 46 is connected to aninput line 48 of the comparison circuit 42 by means of a switch meansgenerally indicated at 49. Thus, selection of inputs to the comparisoncircuits 42 may depend first upon selection of correlation between therotational speed signals or correlation between tension conditionsignals and secondly to selection of particular level or range of suchcorrelation.

The comparison circuit 42 may, by way of example only and not by way oflimitation, take the form of a bridge circuit which compares voltagesignals appearing on the input conductors 41, 48 and produces an errorsignal which is then applied to the conductor 24 to control the firstcontrol means or motor amplifier 20. By such a closed loop system,withdrawal of yarn 12 from the yarn package 14 as demanded for knittingby the needles of the knitting machine is accomplished.

The present invention further contemplates that the operative signalappearing on the conductor 35 from the tension sensor 32 may be employedas a stop motion control over the related knitting machine. That is, theabsence or breakage of the yarn 12 would cause the level of this signalpresent on the output conductor 35 to become indicative of such absenceor breaking and detection of change in the signal may be employed tointerrupt the driving of the knitting machine so as to avoid improperformations of knitted fabric.

In adapting the single yarn arrangement heretofore described to amultiple feed knitting machine, as contemplated by the presentinvention, it is envisioned that an'interconnection for the levelsetting potentiometers 44, 45, 46 might be provided whereby push buttonselection may be made for which of three level setting po- 1tentiometers is to be used in controlling feeding of yarn to particularknitting machine position. That is, the level set by the firstpotentiometer 44 might be selected for a first knitting position; withthe level set by the second potentiometer 45 being selected for a secondposition; the level set by the third potentiometer 46 being selected fora third position, and the fourth position returning to the level set bythe first potentiometer 44. Such an arrangement, with push buttonselection, would facilitate wide selectivity for yarn feeding controland thereby aid in furthering accomplishment of the object of thisinvention.

In the drawings and specification, there has been set forth a preferredembodiment of the invention, and although specific terms are employed,they are used in a generic and descriptive sense only and not forpurposes of limitation.

That which is claimed is:

1. In combination with a knitting machine having a rotating drivemember, a plurality of needles moved by the drive member for knittingfabric and at least one yarn package from which yarn to be knit issupplied to the needles, yarn feeding apparatus comprising:

means interposed between a yarn package and the needles for positivelyengaging a corresponding yarn to be supplied for knitting,

variable speed drive means drivingly connected with said yarn engagingmeans for driving the same in rotation and thereby for withdrawing yarnfrom the corresponding package and feeding the yarn to the needles asrequired for knitting,

first control means operatively connected with said drive means forcontrolling the rotational speed thereof,

tachometer means operatively responsive to said drive means for sensingrotation thereof and for generating a first signal indicative of thespeed of rotation thereof,

rotation means operatively responsive to the drive member for sensingrotation thereof and for generating a second signal indicative of thespeed of rotation thereof,

yarn tension means operatively responsive to tension in the yarn betweenthe needles and said yarn engaging means for sensing tension therein andfor generating a third signal indicative of the level of tensiontherein,

standard means for generating a fourth signal indicative of a desiredlevel of tension, and

means operatively connected with said first control means andoperatively connected with said tachometer means, said rotation means,said tension means and said standard means and including switch meansfor selecting between correlation of said first and second signals andcorrelation of said third and fourth signals and second control meansfor varying the rotation of said drive means in accordance with anydifference from a predetermined correlation between a selected pair ofsignals,

whereby yarn is withdrawn from the corresponding yarn package asdemanded for knitting by the needies.

2. The combination according to claim 1 wherein said yarn engaging meanscomprises a positive grip pulley means for receiving and gripping yarnand further wherein said variable speed drive means comprises a driveshaft upon which said pulley means is fixed for driven rotation.

3. The combination according to claim 1 wherein said variable speeddrive means comprises a electrical servomotor and said first controlmeans comprises electrical circuit means for varying a characteristic ofelectrical current delivered to said servomotor.

4. The combination according to claim 1 wherein said tachometer means,said rotation means, said tension means and said standard means eachgenerate a corresponding electrical signal as said first, second, thirdand fourth signals and further wherein said sec ond control meanscomprises electrical circuit means for generating an error signal whichaccords with any difference from a predetermined correlation between aselected pair of signals.

5. The combination according to claim 1 wherein each of said tachometermeans and said rotation means generate a train of electrical pulses asthe respective first and second signals and further comprising meanselectrically connected with said tachometer means and said rotationmeans for connecting said trains of electrical pulses into analogsignals.

6. The combination according to claim 1 wherein said knitting machine isa circular knitting machine having a cylinder and a main drive gearoperatively connected with said cylinder and operating as said drivemember for driving the cylinder in rotation and thereby for initiatingknitting action of said needles and further wherein said rotation meanscomprises asensor responsive to rotation of said main drive gear.

7. The combination according to claim 1 further comprising meansoperatively connected with said yarn tension means and responsive toexcursions of sensed tension therein outside of a predetermined rangefor interrupting operation of said knitting machine.

1. In combination with a knitting machine having a rotating drivemember, a plurality of needles moved by the drive member for knittingfabric and at least one yarn package from which yarn to be knit issupplied to the needles, yarn feeding apparatus comprising: meansinterposed between a yarn package and the needles for positivelyengaging a corresponding yarn to be supplied for knitting, variablespeed drive means drivingly connected with said yarn engaging means fordriving the same in rotation and thereby for withdrawing yarn from thecorresponding package and fEeding the yarn to the needles as requiredfor knitting, first control means operatively connected with said drivemeans for controlling the rotational speed thereof, tachometer meansoperatively responsive to said drive means for sensing rotation thereofand for generating a first signal indicative of the speed of rotationthereof, rotation means operatively responsive to the drive member forsensing rotation thereof and for generating a second signal indicativeof the speed of rotation thereof, yarn tension means operativelyresponsive to tension in the yarn between the needles and said yarnengaging means for sensing tension therein and for generating a thirdsignal indicative of the level of tension therein, standard means forgenerating a fourth signal indicative of a desired level of tension, andmeans operatively connected with said first control means andoperatively connected with said tachometer means, said rotation means,said tension means and said standard means and including switch meansfor selecting between correlation of said first and second signals andcorrelation of said third and fourth signals and second control meansfor varying the rotation of said drive means in accordance with anydifference from a predetermined correlation between a selected pair ofsignals, whereby yarn is withdrawn from the corresponding yarn packageas demanded for knitting by the needles.
 2. The combination according toclaim 1 wherein said yarn engaging means comprises a positive grippulley means for receiving and gripping yarn and further wherein saidvariable speed drive means comprises a drive shaft upon which saidpulley means is fixed for driven rotation.
 3. The combination accordingto claim 1 wherein said variable speed drive means comprises aelectrical servomotor and said first control means comprises electricalcircuit means for varying a characteristic of electrical currentdelivered to said servomotor.
 4. The combination according to claim 1wherein said tachometer means, said rotation means, said tension meansand said standard means each generate a corresponding electrical signalas said first, second, third and fourth signals and further wherein saidsecond control means comprises electrical circuit means for generatingan error signal which accords with any difference from a predeterminedcorrelation between a selected pair of signals.
 5. The combinationaccording to claim 1 wherein each of said tachometer means and saidrotation means generate a train of electrical pulses as the respectivefirst and second signals and further comprising means electricallyconnected with said tachometer means and said rotation means forconnecting said trains of electrical pulses into analog signals.
 6. Thecombination according to claim 1 wherein said knitting machine is acircular knitting machine having a cylinder and a main drive gearoperatively connected with said cylinder and operating as said drivemember for driving the cylinder in rotation and thereby for initiatingknitting action of said needles and further wherein said rotation meanscomprises a sensor responsive to rotation of said main drive gear. 7.The combination according to claim 1 further comprising meansoperatively connected with said yarn tension means and responsive toexcursions of sensed tension therein outside of a predetermined rangefor interrupting operation of said knitting machine.